Partway through Hawking, a moving new PBS documentary on the life and work of British physicist Stephen Hawking, narrated via voice synthesizer by the man himself, Hawking raises a delicate point. “Sometimes I wonder,” he says, “If I’m as famous for my wheelchair and disabilities as I am for my discoveries.” He never offers a definitive answer, but it seems pretty clear that the filmmakers think it’s mostly about the discoveries.

Sure, the backstory is poignant, and even amazing—diagnosed with the muscle-wasting condition known variously as ALS, Lou Gehrig’s Disease and, in the U.K., motor neurone disease, Hawking was given just two years to live. Yet a full half-century later, after a distinguished career at Cambridge, the 71-year-old scientist, now utterly paralyzed, is still hard at work trying to solve the mysteries of the universe.

But it’s the discoveries that really catapulted Hawking into the pantheon of physics greatness, right? Trapped in an increasingly useless body, he could, as Caltech physicist Kip Thorne says in the film “move at lightning speed through the universe, seeing things nobody else could see.” He is, as most of us know, the greatest physicist since Einstein.

Except that he isn’t. “Rubbish,” Hawking himself responded, when I posed this proposition to him during a 1993 interview. “It’s mere media hype.” It’s undeniable that Hawking has made key contributions to both relativity and quantum physics. He came up with the insight that the Big Bang emerged from a singularity, a point so small and dense that the very laws of physics can’t describe it. He figured out what happened when black holes merge. He also came up with the startling and counter-intuitive notion that black holes can evaporate, slowly at first, then faster and faster until they explode—an idea that was at first ridiculed, but which is now mainstream. “This result,” says Bernard Carr, one of Hawking’s former PhD students, “unified relativity and quantum theory and thermodynamics.”

That would be positively mind-blowing—if true. But it’s really not: the so-called “Hawking radiation” that should emerge from black holes draws on those disparate areas of physics, but “unify” means something else entirely. Unifying relativity and quantum physics is something Einstein tried to do for the last two decades of his life, and failed. The best bet for unification these days is string theory—assuming it turns out to be correct, which we may never know.

You can’t blame Hawking for that over-the-top quote, but Hawking himself talks about the honor he felt being inducted into the Royal Society. “My name,” he says “sat alongside Isaac Newton and Charles Darwin.” Well, yeah, and also along a lengthy list of other scientists you’ve never heard of.

Then there’s A Brief History of Time, Hawking’s mega-bestseller, first published in 1988. “I wanted the book to be read by millions of people around the world like a bestselling airport novel,” he says in the film. “I felt the mass market wanted to know how the universe began.” Fat chance, thought his agent and his publishers—but Brief History went on to sell millions upon millions of copies. The reason was that it explained some of the great mysteries of the cosmos in simple, digestible language. “It made this subject a topic of conversation among all walks of life,” says Caltech’s Thorne.

Surely you remember all those conversations. Or…maybe not. In fact, the book was nearly incomprehensible to people in all walks of life outside of theoretical physics. The real story, suggested Time book critic Paul Gray in a 2001 essay, is that “people buy a book for many reasons: either they want to read it, think they ought to read it, or want to impress people by making them think they have read it.” Whether they actually do read it is an entirely different question.

None of this should suggest that Stephen Hawking is not one of the world’s leading physicists: he is, and would still be even if he were perfectly healthy. It’s the disability, though, and his fierce determination to carry on regardless, that makes the film so engaging and his life so uplifting—and perhaps makes people want to overstate his accomplishments. He is, one former student says, “the most stubborn person I know.”

Hawking chronicles that stubborn streak through Hawking’s own memories and through those of his sister, his first wife, and many, many colleagues. You don’t hear from his second wife, though: she was one of his former nurses, whom he ultimately divorced after 11 years of marriage amid scandalous rumors. “The press printed unsubstantiated allegations,” he says, “that I had been the victim of domestic violence. This was a gross invasion of our privacy.” (He doesn’t say, however, that it didn’t happen.)

The film is peppered with photos and videos of Hawking as a young boy, then a nerdy Oxford undergrad, then an increasingly disabled man who can now only twitch the muscles in his cheek to operate a computer and voice synthesizer. There’s also plenty of cheesy footage of actors recreating what Hawking might have looked like writing on a blackboard way back when—an unfortunate technique that’s now evidently de rigeur in historical documentaries.

You also see flashes of Hawking’s sense of humor. It shows in his willingness to spoof his own smartest-man-on-the-planet brand with appearances on The Simpsons and Star Trek, and with his collaboration with Jim Carrey on a stunt call while the comedian was on the air with David Letterman (“I’m watching Dumb and Dumber, Jim, and you’re a genius.” “No, Stephen, you’re a genius.” “No, Jim, you are”). He’s also pretty funny in real life. “It’s a pity,” he says to a huge audience at a public talk, “that nobody has found an exploding black hole. If they had, I would have won a Nobel prize.” He delivers the line for laughs, and gets them.

And then there’s something that doesn’t make it into the film, but which I saw myself when I interviewed him in 1993. It was in Seattle, where he’d gone to give some talks, and his aide let it slip that whenever he traveled, he would ask his hosts to set up a meeting with local children with disabilities.

These visits were totally unpublicized, but I was lucky enough to go along and watch the pretty-great physicist answered questions from a half-dozen or so kids for an hour, their wheelchairs arrayed around his in a semicircle. That’s when I became convinced that even when you strip away the hype, Stephen Hawing may not be the world’s greatest living physicist—but he’s a pretty extraordinary human being.